Composite Failure Assessment in Different Filling Techniques using SS-OCT

Objectives: Gap formation and lack of adaptation still accompany dental composite restorations. Non-destructive assessment and monitoring of these phenomena are essential. Thus, the aim of this study is to assess gap formation in different filling techniques at the tooth-restoration interface using a novel technique; swept source optical coherence tomography (SS-OCT). Methods: Cylindrical class-I cavities (3 mm in diameter and 1.5 mm in depth) were prepared in the occlusal surface of 30 human premolar teeth. The specimens were divided into two groups according to the adhesive system used; Clearfil SE Bond (Kuraray Medical, Tokyo, Japan) or Tokuyama Bond Force (Tokuyama Dental, Tokyo, Japan). Each adhesive was applied in three sub-groups according to the filling techniques; one sub-group was restored by lining the cavity floor using a flowable composite Palfique Estelite LV followed by bulk filling technique using a universal composite Estelite Sigma Quick (both by Tokuyama Dental), while in the second and third sub-groups, bulk and incremental filling techniques were performed using Estelite Sigma Quick. Ten serial cross-sectional images of the whole restored cavity were obtained non-invasively by SS-OCT (Santec, Japan) at 1310nm center wavelength. An image analysis software was used to measure cavity floor gap length at each cross-section, which appeared as bright clusters at the bonded interface of the cavity floor and to compare the different filling techniques. Results: Two-way ANOVA showed that both factors; filling technique and adhesive, and their interaction were significant (P < 0.05). While incremental filling technique improved adaptation for Bond Force, for SE Bond there was no significant difference among the techniques. Conclusion: Apart from the filling technique, the adhesive material played a major role in cavity adaptation, with the two-step self-etching material showing superior results. SS-OCT is a non-invasive technology that can detect and quantify micrometer gaps at the bottom of composite restorations.